1. Field of the Invention
The present invention relates generally to video tracking systems and, more particularly, to a method for selecting a target in an automated video tracking system.
2. Prior Art
For purposes of this disclosure, automated tracking is defined as the automatic control of the Pan, Tilt and Zoom (PTZ) motors of a movable PTZ camera so as to keep the camera view centered on a designated, moving target. Automated tracking as defined is used in a number of different applications areas, such as surveillance and security monitoring. In this area, the target is usually a human.
Automated tracking systems typically have several parts, target selection, model generation, and camera control. A target needs to be selected for tracking. This can be via an operator or via an automated motion detection module or other intruder detection system. An internal xe2x80x9cmodelxe2x80x9d of the appearance of the target is necessary to allow the tracking system to find the target in subsequent images. A camera motion control model is necessary to determine how to move the camera to keep the target in the center of the field of view.
The present disclosure relates to the problem of target selection. Identification of potential tracking candidates (i.e., a desired target) in a video scene is typically not part of the function of an automated tracking system. For instance, in the area of surveillance, target selection requires a lot of background knowledge about the objective of any surveillance application. What looks xe2x80x9csuspiciousxe2x80x9d in one surveillance application, e.g. a retail store, may not look suspicious in another, e.g. a parking lot.
In some applications, any source of motion is suspicious, e.g., monitoring a warehouse at night. In that case, an intrusion detection sensor, or a motion sensor, could be used to designate a target for tracking. A more sophisticated automatic monitoring system, could be used to designate targets for certain other applications, as long as the rules to select targets can be clearly enumerated and implemented. However, in general, it is expected that a human operator will indicate the target to the tracking system.
When an operator designates a person in the video image as the tracking system""s target, there is a subtle difference in meaning between the operator""s and the tracking system""s concept of the target. The operator is designating a person as the target, however, the tracking system is simply accepting a region of the image as the target. Because of this, the operator may not be overly fussy about what part of the person he picks, since after all, its clear to any (human) observer which person he or she selects. Furthermore, the tracking system will form a target model based on exactly what image region the operator selected. As it has no independent knowledge of the desired target it cannot generalize beyond what it is told. Further problems arise because the operator is selecting a moving target, therefore he or she may select a bad target, a portion of a target, or possibly even an empty space.
Therefore it is an object of the present invention to provide a method and apparatus for selecting a target in a video tracking system which resolves the problems with the prior art video tracking systems.
Accordingly, a method for selecting a target in an automated video tracking system is provided. The method comprises the steps of: displaying video image data of a scene having a target to be tracked; freezing the video image data to display a frame thereof; and selecting a desired target in the frame of the video image data. Preferably, the method further comprises the steps of: unfreezing the video image data after the selecting step; and tracking the selected desired target in the unfrozen video image data.
The selecting step preferably comprises drawing a shape, such as a rectangle around at least a portion of the desired target with a input device, such as a computer mouse. Alternatively, the selecting step comprises indicating a region in which the desired target resides with an input device, such as using a computer mouse to click on the region.
Also provided is an apparatus for selecting a target in an automated video tracking system. The apparatus comprises: a camera for providing video image data of a scene having a desired target to be tracked; a display for displaying the video image data; means for freezing the video image data to display a frame thereof; and an input device for selecting the desired target in the frame of the video image data. Preferably, the apparatus further comprises: means for unfreezing the video image data after the desired target is selected; and an automated video tracking system having a controller for controlling the camera to track the selected desired target in the unfrozen video image data.
The input device preferably comprises means for drawing a shape, such as a rectangle around at least a portion of the desired target. Alternatively, the input device comprises means for indicating a region in which the desired target resides, such as by clicking on the region. Preferably, the input device is a computer mouse.
Also provided is a video tracking system comprising: a camera for providing video image data of a scene having a desired target to be tracked; a display for displaying the video image data; means for freezing the video image data to display a frame thereof; an input device for selecting the desired target in the frame of the video image data; means for unfreezing the video image data after the desired target is selected; and a controller for controlling the camera to track the selected desired target in the unfrozen video image data.
Preferably, the input device comprises means for drawing a shape, such as a rectangle, around at least a portion of the desired target. Alternatively, the input device comprises means for indicating a region in which the desired target resides, such as by clicking on the region. Preferably, the input device is a computer mouse.